Polarisation Filter

[pdmoylan]

The density of a single polarizer, circular or linear, does not change as you rotate it. It always passes the same amount of light, regardless of its rotation.

Perhaps in theory, but not my experience. Max polarization = greatest light loss. Try it with any camera.

[Alan Klein]

The density of a single polarizer, circular or linear, does not change as you rotate it. It always passes the same amount of light, regardless of its rotation.

So if the polarizer filter mfr recommends 1 1/2 stops loss, just use that amount regardless?

[Bob Salomon]

So if the polarizer filter mfr recommends 1 1/2 stops loss, just use that amount regardless?

Good place to start. Do a test.

[LabRat]

Some things I learned on many pro car shoots I have worked on is that car designers actually design body surfaces to reflect light to give surfaces "body" and form... That light is a key ingredient to the design and surfaces... Designers have very complex software that simulates light from a multitude of angles so overall appearance is even from many as possible viewing angles... Without the light, areas tend to look "naked" and surface volume changes, even to the point where raised areas can look depressed or unfinished... So, for body work, usually all surfaces will be lit, or at least some reflector card etc will be reflecting some light energy off subject and back to camera...

Polarization can cut one area, but not another plane in the shot, so not usually used, and can form unwanted patterns in polarized areas (esp glass), and bring out usually invisible surface issues... And highlights/reflections (like on glass) can look weird...

So, I'm mentioning that the solutions involve adding more even light until balances are achieved... Usually, this involves even light from tenting, and strategically placed lighter and darker large fill cards to apply broad illumination...

One cheat that's applied often is shooting very early or late in the day where the sky before sunrise/after sunset is used to light the side of a vehicle, camera is low, so top is not seen clearly, slightly darker, and blue skylight flows off top with a deeper blue color (think Jeep on a mountaintop look ads)...

Cars can be tough, but if you follow a plan to apply broad, even light, can be quite manageable...

Good luck!!!!

Steve K

[Bernice Loui]

One of the prime aspects of car styling/design has much to do with reflections, shadows, textures and more coupled with how light interacts with these sculptured shapes. Car Fotos should enhance or capture the car stylist intent of visual expression. Applying a polarizer to cut/reduce these reflections could be counterproductive to the original styling of the car as the car's stylist-designer intended. Typically, a VERY large diffused light source is used combined with reflectors (white, off-white, silver, gold or _) where needed or negative fill (black often velvet material) is applies where reflective light control is needed.

Back in the color transparency with 4x5 sheet film car images like these demanded phenomenal strobe power often in the five digits of watt/seconds distributed evenly across the diffuser "light bank" due to the large area being lighted and diffusion. Found an example on the web:
https://macbethstudio.com/blog-home/...ead-light-bank

Not only did the diffused light bank have phenomenal strobe power, color temperature of the lighting MUST be correct for the color transparency film used, E6 processing and every aspect of the image making system involved to reveal accurate and precise color rendition of the car being imaged. Exposure/film density is a precise given.

One alternative is to exploit outdoor light near sunrise or sunset. When the weather and sun conditions are correct, the effective lighting can work as an effective light source that enhances the reflective surface shapes designed into the car body. Found this example done some time in the late 1980's _ early1990's of a Saab 9000T once owned. Using a 5x7 Sinar C, 8 1/2" Commercial Ektar @ f16 (camera movements as needed), Kodak Ektachrome film, E6 processing at The New Lab in San Francisco. Note the colors of the sunset is reflected to the imaging system over powering the metallic blue of the Saab 9000T and how the reflections from the car body's shape interacts with the ligting.






Lighting often makes enough difference to put lens, camera, film, post processing and .. secondary.

Bernice

Some things I learned on many pro car shoots I have worked on is that car designers actually design body surfaces to reflect light to give surfaces "body" and form... That light is a key ingredient to the design and surfaces... Designers have very complex software that simulates light from a multitude of angles so overall appearance is even from many as possible viewing angles... Without the light, areas tend to look "naked" and surface volume changes, even to the point where raised areas can look depressed or unfinished... So, for body work, usually all surfaces will be lit, or at least some reflector card etc will be reflecting some light energy off subject and back to camera...

Polarization can cut one area, but not another plane in the shot, so not usually used, and can form unwanted patterns in polarized areas (esp glass), and bring out usually invisible surface issues... And highlights/reflections (like on glass) can look weird...

So, I'm mentioning that the solutions involve adding more even light until balances are achieved... Usually, this involves even light from tenting, and strategically placed lighter and darker large fill cards to apply broad illumination...

One cheat that's applied often is shooting very early or late in the day where the sky before sunrise/after sunset is used to light the side of a vehicle, camera is low, so top is not seen clearly, slightly darker, and blue skylight flows off top with a deeper blue color (think Jeep on a mountaintop look ads)...

Cars can be tough, but if you follow a plan to apply broad, even light, can be quite manageable...

Good luck!!!!

Steve K

[xkaes]

Good place to start. Do a test.

I agree with Bob. Much depends on how you meter -- incident vs reflectance. If you use a TTL meter you will see a change in the exposure as the PL is rotated. If there is a lot in the scene impacted by polarized light it will make a BIG difference and vice versa. Do you want the elimination of polarized glare to change your exposure? If you do, you're probably not metering the subject correctly. When I meter a scene, I want to meter it without the glare -- that's one of the reasons I use incident metering.

[r.e.]

How to photograph an Aston Martin without CGI, substance from 07:00. Finished photographs at https://www.andreiduman.com/Automotive/thumbs.

Camera: medium format with a PhaseOne back.

[r.e.]

This is a short BTS video for the above Eizo webinar:

[Doremus Scudder]

Several techniques I used to manage proper exposure:

1. I employed use of a 35mm film or digital camera as a meter, placing a Pola filter on that camera.
2. Since exposure loss with pola filters changes markedly to the extent you change amount of polarization, you will have to set the filter to where you see the changes you want in the scene and meter accordingly.
3. Place a comparable pola filter on the LF lens and adjust the amount of polarization to how you set it with the 35mm.
4. Experiment prior to calibrate exposure readings with the LF results. I had a 90mm f8 Nikkor which was always .5 stops darker than the exposure determined with the 35mm. My other lenses needed no adjustment.
5 so this process a. Eliminates having to exposure compensate for the pola filter but you will have to adjust exposure for any calibration differences.
6. Even with the best pola filters, I found color issues when using them in very low light, but this is particularly true with modern day digital cameras.
7. I found old tiffen linears to be somewhat neutral whereas Nikons tended towards blue (cooler) and calumet towards green.
8. Set your pola filter to neutral setting at first and watch change as you turn it. You may find that the slight polar effect at neutral position is sufficient. There is a marked difference between unfiltered clvs neutral position.
9. As Drew mentioned, using pola filters on artificial lighting in addition to on the lens may give you a denser look, something to experiment with.
10. I expect there are other methods of determining exposure compensation for pola filters, but they are not all the same regarding amount of light loss, particularly with the HR thin filters being made now.
11. The range of light loss I found to be between 2/3 and 1.5 stops depending on how much you turn that filter.

I see no reason to go to such complicated lengths to expose through a polarizer.

Just meter through it with your trusty spot meter with the filter oriented to give you the amount of polarization you desire. No need for using a 35mm camera as a meter...

If there is a discrepancy between the meter reading through the polarizer and the actual results, this will be made abundantly clear from your careful field notes. If it is consistent, add an exposure factor to your through-the-filter reading.

Polarizing filters don't change the colors in the scene enough to not simply meter through the filter.

If you shoot color transparency materials, you need to invest in a high-quality polarizer that has little color cast and/or add the appropriate CC filtering when using it.

And, it's easy to determine how a polarizer will render a scene; simply look through it... EZPZ.

Best,

Doremus

[Peter De Smidt]

My experience matches Steve's. We did a lot of the photo work for Pierce fire trucks, Oshkosh Truck, ..... Back in the film days, they were mostly photographed in a large cyclorama, where the entire ceiling was a controllable light source.....These days, they are often photographed in a parking lot using many exposures, all pieced together in post, just like interiors for Gulfstream planes.